夏季西太平洋台风频数异常与ENSO事件的关系及大气环流异常特征

RELATIONSHIP BETWEEN SUMMER TYPHOON FREQUENCY ANOMALIES IN WESTERN PACIFIC AND ENSO EVENTS,AND THE ANOMALOUS ATMOSPHERIC CIRCULATION CHARACTERISTICS

根据西太平洋编号台风资料、NOAA卫星观测OLR资料和NCEP/NCAR风场再分析资料,在统计和探讨夏季西太平洋台风多(少)发年与ENSO事件的关系的基础上,分别对夏季台风异常偏多或偏少的ElNi?o、LaNi?a年的OLR特征量和热带夏季风环流进行合成对比分析。分析表明:夏季当南半球马斯可林高压和澳大利亚高压无明显的系统性异常时,Walker环流异常的影响占主导作用,并遵循ENSO事件对大气环流及台风频数影响的基本规律。若ElNi?o期间澳大利亚高压环流出现系统性异常时,南半球环流异常的影响则占主导地位,台风反而异常偏多。对于1999年LaNi?a特殊年份,马斯可林高压异常偏强引发的季风西风偏北偏东,台风反而异常偏少。弱风速垂直切变区、西太平洋暖池和季风槽的重叠部分是台风频发源地,本文分别对ElNi?o、LaNi?a台风异常偏多(少)年台风频发源地的位置和范围作了比较分析。

By using data of serially numbered typhoons in northwestern Pacific and NOAA OLR data and NCEP/NCAR reanalysis data of wind field, based on the statistics and study of the relationship between the calendar years with more （or fewer） summer typhoons and ENSO events, we compared the composites of OLR eigenvectors and tropical summer wind fields during E1 Nino and La Nino events with more or fewer than normal summer typhoons, respectively. The results show that, in summer, without remarkable systematic anomalies of Mascarene High and Australia High in South Hemisphere, the anomaly of Walker circulation will dominate and follow the rule of ENSO impacts to atmospheric circulation and typhoon frequency. Otherwise, when systematic anomalies of Australia High appear during the E1 Nino events, circulation anomalies in the South Hemisphere will dominate, and many more typhoons will occur. In 1999, which is a special year of La Nifia events, northward and eastward monsoon was induced by the stronger Mascarene High, and fewer typhoons arose. The typhoon source are regions where weak vertical wind shear, warm pool in western Pacific and the area with monsoon troughs are overlapping with each other. Finally, this paper analyzes and compares the source locations and ranges of more （fewer） typhoons in the events of E1 Nino and La Nino, respectively.